WO 2008/053014 describes several possible sequences of manufacturing steps to produce a two-part metal closure. In the manufacture of the two part closure of FIG. 2 of WO 2009/115377, it is desirable to form a profile comprising an inward curl and lugs at the lower end of a thin sheet-metal ring, and to inwardly curl the upper end of the ring, to retain a panel part moveably between the upper and lower ends of the ring. It is also desirable to accurately curl and reduce the diameter of a panel part in as few manufacturing operations as possible.
Conventional methods of forming curls and lugs on metal closures are well known, and the method shown in GB 2149388 (ANCHOR HOCKING CORPORATION) is one example. Conventional methods are suitable for one-part closures having an end panel and sidewalls, wherein the apparatus is able to push against the end panel. This ability is important for loading the closure into the apparatus, for supporting it to avoid unwanted deformation, whilst forming loads are applied, and for unloading it from the apparatus after forming the lugs and curl. However, the ring of the present invention corresponds to that of a closure of the type described in WO 2009/115377 (CROWN PACKAGING TECHNOLOGY, INC) (which is in the same name as the current applicant), and which therefore has no end panel to push against.
EP 0921878 B (IMPRESS METAL PACKAGING GMBH) shows the use of a tool segment with an annular shoulder to push a cylinder segment into an arrangement of forming tools. The cylindrical wall of the cylinder segment is almost entirely inwardly formed and thus the formed cylinder segment is easy to remove when the tools are moved apart.
In contrast, to form the curl and lugs of a closure ring of the type described in WO 2009/115377 (CROWN PACKAGING TECHNOLOGY, INC), it is necessary to support the cylindrical wall during forming and the cylindrical wall of the formed ring also remains engaged in contact with the cylindrical pushing tool after forming.